Chemistry 1- The Earths Atmosphere
Earths atmosphere
About 80% Nitrogen
About 20% Oxygen
Carbon dioxide, water vapour and noble gases eg argon in much smaller portions
Percentage of oxygen in air can be measured by passing known amount of air over hot copper and measuring decrease in volume as oxygen reacts with it
Copper+Oxygen-> Copper Oxide
2Cu+02->2CuO
Gas syringes- measure volume of gas in experiment
Usually 100cm3
Oxygen in tube can react in copper making results less accurate
Let cool down afterwards
Believe earth was formed 4.5 billion years ago
Early atmosphere probably formed from gases given out by volcanoes- lot of volcanic activity
Early atmosphere probably mostly carbon dioxide with little or no oxygen, small portions of water vapour, ammonia, and methane
As earth cooled water vapour condensed forming oceans
Mars and Venus atmospheres similar to early earths atmopshere
Many theories to how life began
One theory- interaction between hydrocarbons, ammonia and lightning
Stanley Miller and Harold Urey carried out experiments and published findings in 1953
Aim to see how substances now made from living things could be formed in conditions thought to have existed on the early earth
Mixture of water, hydrogen, methane and ammonia in sterile flask
Mixture heated to evaporate water to produce water vapour
Mixture heated to evaporate water to form water vapour
Electric sparks passed through mixture of water vapours and gases, stimulating lightning
After week amino acids the building blocks for proteins were found
Supported 'primordial soup' theory- complex chemicals needed for living things can be produced naturally on earth
Plant and algae carry out photosynthesis uses carbon dioxide to produce oxygen, appearance of plant and algae increased oxygen production
Carbon dioxide also dissolved in oceans, was used in the production of sedimentary rocks such as limestone, and the production of fossil fuels from the remains of dead plants and animals
Burning of fossil fuels is adding more carbon dioxide to the atmosphere that can be removed
Level of carbon dioxide in atmosphere is increasing accounting to global warming
Oceans becoming more acidic as they dissolve increasing carbon dioxide levels- has impact on aquatic animals
Oxygen and nitrogen can be separated by fractional distillation
Air filtered to remove dust, cooled in stages till it reaches -200 degrees centigrade- liquid at this temperature- air been liquified
Water vapour condenses and removed by absorbent filters
Carbon dioxide freezes at -79 degrees centigrade
Oxygen liquefies at -183 degrees centigrade
Nitrogen liquefies at -196 degrees centigrade
Liquid nitrogen and oxygen separated by fractional distillation - nitrogen released at top as gas, liquid oxygen at bottom
Liquid nitrogen used to freeze foods, food packaged with gas nitrogen and oil tanks flushed with them, oxygen used in manufacture of steel and medicine